1. Field of the Invention
This invention relates to towable stream gauge platforms and in particular to a towable stream gauge platform having an asymmetrical elastic harness which causes a submerged hydroboard to pursue an upward twisting path toward the surface.
2. Discussion of the Prior Art
Floating towable stream gauge platforms are used to survey river courses and to gauge river and stream discharge rates using Doppler sonar measuring instruments. For purposes of brevity, and without being limiting, this disclosure will refer to towable stream gauge platforms as “hydroboards” or “boards” as they are commonly referred to in the art.
Hydroboards are modified forms of recreational boogie boards adapted to carry surveying equipment for measuring the contours or discharge rates of a body of running water. An aperture is provided centrally in the board in which a surveying instrument capable of measuring depth and velocity can be secured as with a band clamp. A hydroboard is usually towed using a flexible harness which is designed to accommodate the impact on the board of waves and currents.
A hydroboard will map the contours of a waterway by pulling it along the water's course. Alternatively, a hydroboard can be used to gauge discharge rates of a flowing body of water by retaining it from a stationary structure spanning the waterway being measured, such as a bridge. The hydroboard can be caused to traverse the waterway by crossing the spanning structure from one bank of the waterway to the other, during which the surveying equipment supported on the hydroboard measures water velocity at multiple depths. The sum of the measurements made as the equipment traverses the waterway gives a measure of the total flow.
A recurrent problem encountered when using hydroboards as described above is that the nose of the hydroboard may dip under the surface of the water in which case the hydroboard can rapidly submerge. Since the hydroboard is generally deployed at the end of a tow rope retained from in front of and above the board, the harness or tow line may snap resulting in not merely loss of the hydroboard but the expensive surveying equipment deployed on it.
Prior art hydroboards have typically been constructed using rigid polystyrene (or rigid polyethylene for boats). Thus, when the nose of a prior art hydroboard dips underwater, the board acts as an inflexible underwater sail causing the board to submerge rapidly.